Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $56.68   10.580%   $62.6767   $62.68   $62.70   $62.70  
  Purchase #2 $44.68   5.562%   $47.1651   $47.17   $47.15   $47.20  
  Purchase #3 $27.98   7.777%   $30.156   $30.16   $30.15   $30.20  
  Purchase #4 $157.31   7.581%   $169.2357   $169.24   $169.25   $169.20  
  Purchase #5 $56.44   6.584%   $60.156   $60.16   $60.15   $60.20  
  Purchase #6 $12.71   10.322%   $14.0219   $14.02   $14.00   $14.00  
  Purchase #7 $162.70   13.166%   $184.1211   $184.12   $184.10   $184.10  
  7 purchase totals = $518.50       $567.5325   $567.55   $567.50   $567.60